Publication Citation: Case Against Optical Gauge Block Metrology

The current definition of length of a gage block is a very clever attempt to evade the systematic errors associated with the wringing layer thickness and optical phase corrections. In practice, there are very large systematic operator and surface effects which cause systematic errors and most laboratories wring blocks to quartz or fused silica. We present quantitative data on these effects and show through detailed uncertainty budgets that the current definition of gage block length is the primary source of measurement uncertainty. For comparison, an uncertainty budget for gage block calibration by mechanical contact is presented.